Here‚Äôs a basic grammar question that baffled an adequately English-savvy friend of mine: Why are the nominative case and subjective case lumped as just a single case in English? Plus the objective case and possessive case, shouldn‚Äôt there be four cases in all?

To answer my friend‚Äôs question, I came up with this simplified layperson‚Äôs definition of case: it is the form a noun or pronoun takes to indicate its functional relationship to other words in a sentence or clause. In modern English, there are indeed only three cases‚ÄĒthe nominative or subjective, classified as just a single case, when the noun or pronoun acts as the subject of a sentence or clause; the objective case, when the noun or pronoun receives the action of the verb or is the object of a preposition; and the possessive case, when the noun or pronoun shows possession of something.

Now let‚Äôs find out why the nominative and subjective are considered as just one case and practically synonymous.

A telltale sign that a noun or pronoun is in the nominative case is when it‚Äôs functioning as the subject of a verb in a sentence or clause. It‚Äôs not necessarily the doer of the action of that verb, for that‚Äôs true only when the sentence or clause is in the active voice.

In the active-voice sentence ‚ÄúThe committee planned the Pope‚Äôs itinerary,‚ÄĚ for instance, the subject ‚Äúcommittee‚ÄĚ is the doer of the action of the verb ‚Äúplanned‚ÄĚ; as such, that subject is in the nominative case. But see what happens when that sentence is rendered in the passive voice: ‚ÄúThe Pope‚Äôs itinerary was planned by the committee.‚ÄĚ Here, the doer of the action of the verb‚ÄĒ‚Äúthe committee‚ÄĚ‚ÄĒis no longer the subject of the sentence; instead, the receiver of that action‚ÄĒ‚Äúthe Pope‚Äôs itinerary‚ÄĚ‚ÄĒhas become the subject of the sentence.

Thus, whether a sentence or clause is in the active or passive voice, the noun or pronoun that serves as its subject will always be in the nominative case. So when is a noun or pronoun in the subjective case instead?

By definition, a noun or pronoun is in the subjective case when it is in the subject position of a sentence or clause. As such, it‚Äôs either (a) a subject that ‚Äúdid‚ÄĚ or is ‚Äúdoing‚ÄĚ something, as in ‚ÄúThe police cordoned Rizal Park,‚ÄĚ or (b) a subject not doing something but only being described in a certain way, as in ‚ÄúThe police is ready for the Pope‚Äôs visit.‚ÄĚ

With ‚Äúthe police‚ÄĚ as subject of the sentence either way, it clearly also meets the criterion for nouns in the nominative case. Indeed, whether in the nominative case or subjective case, a noun or pronoun always functions as the subject of a sentence or clause. It is precisely for this reason that the two cases are virtually synonymous and folded into just a single case.

However, we must keep firmly in mind that only when the subject of a sentence is specifically a noun will there be no grammatical difference between its nominative and subjective forms. This is because nouns in modern English don‚Äôt inflect or change form at all in both the nominative and subjective cases and in the objective case as well.

In contrast, the pronouns‚ÄĒparticularly the personal pronouns‚ÄĒtypically inflect for different grammatical cases. Consider this sentence with a nominative subject: ‚ÄúThe committee members approved the security plan.‚ÄĚ That subject can be routinely replaced with the nominative pronoun ‚Äúthey‚ÄĚ: ‚ÄúThey approved the security plan.‚ÄĚ

But see what happens when that sentence is rendered in the passive voice: ‚ÄúThe security plan was approved by them.‚ÄĚ The nominative pronoun ‚Äúthey‚ÄĚ has inflected or changed into the objective pronoun ‚Äúthem.‚ÄĚ

We will explore the inflections of the various personal pronouns for the various cases in a subsequent column.

Next: How the English personal pronouns inflect for case (on Tuesday, January 31, 2017)